Metal nanostructures play an important role in many fields, such as nano-optics, biochemical sensor, precision optical instruments with ultra-high resolution imaging, surface plasma, and surface plasma lithography. In the prior art, metal nanostructures can be made by lift-off process, milling process of focused ion beam, or electrochemistry method. However, since the above methods can introduce chemical reagents, it is difficult to achieve a nanostructure having a specific morphology. So it is a challenges to make a metal nanostructure having a specific morphology.
In the processing of nanostructures, the rate of chemical corrosion depends on the chemical properties of materials. For example, since different crystal orientations of silicon have different corrosion rates, a specific silicon three-dimensional nanostructure can be obtained. However, it is difficult to obtain specific three-dimensional nanostructures for most metal crystals by chemical corrosion. Dry etching methods include reaction ion etching (RIE) method and inductively coupled plasma etching method. The rate of dry etching depends on the reaction surface of ions. The etching rate of the reaction surface is greater than the etching rate of the other surfaces. A specific nanostructure can be obtained by reasonable etching rate ratios. The focused ion beam induced etching (FIBIE) method is also one of the dry etching methods for preparing three-dimensional nanostructures. However, only inclined trough structures can be obtained by the FIBIE method, and the sizes of the inclined trough structures are too large and it is difficult to obtain etching masks. Furthermore, it is particularly difficult to obtain three-dimensional gold nanostructures.
What is needed, therefore, is to provide a method for making a pine shaped metal nano-scaled grating for solving the problem discussed above.